A system is known from patent application FR 2 803 447 for generation of power for a motor vehicle on-board network. This system comprises a three-phase alternator which is associated with a three-phase inverter. Electronic control means carry out the voltage regulation by modulation of the control pulse width.
In general, and in particular in systems of the aforementioned type, it is necessary to maintain the voltage of the on-board network at a required value, for example at approximately 14 Volts.
When the motor vehicle is at a standstill (combustion engine running), the alternator rotates at a reduced speed, for example at approximately 800 rpm, in order to minimise the fuel consumption.
A substantial requirement for electric charge, in particular as a result of switching on an electrical apparatus of the on-board network, such as the air-conditioning system, then gives rise to a requirement for torque which can be excessive, and can cause the combustion engine to stall.
In order to avoid an excessive requirement for torque which can provoke stalling of the combustion engine, the alternator is controlled so as to increase the output current of the alternator, firstly according to a step or jump selected in order to supply a sufficient minimum current in a controlled manner at the moment of the requirement for charge, then progressively according to a certain gradient, until the regulation voltage required in order to satisfy the requirement for charge is reached.